1. Technical Field
The present invention relates to semiconductor device fabrication and, more particularly, to forming structures with sidewall image transfer using a spin-on hardmask.
2. Description of the Related Art
With current immersion lithographic techniques using 193 nm light, a minimum pitch size between features is about 80 nm. Techniques such as sidewall image transfer allow the formation of structures below the 80 nm. In conventional SIT, sidewalls are formed around one or more mandrel structures on a surface. The mandrels are then removed, leaving the sidewalls standing free on the surface. This allows the sidewalls themselves to be used to be used as a mask for further processing, allowing the creating of features with widths substantially smaller than the minimum size allowed by a given lithographic process. However, conventional SIT processes are limited in the density of structures that they can produce. While SIT can be performed multiple times, patterning costs increase and overlay rules grow more complicated as additional pattern cycles are introduced.